Objective:
Seasonal reproductive inefficiency is globally observed within the swine industry. Even when photoperiod and temperature are controlled, reductions in pregnancies and subsequent farrowing rates are noted. The most obvious contributor to this phenomenon is the young female. In all likelihood, we see greater effects of seasonality on the young dam as a result of her innate nature to care for herself first and foremost before imparting energies into fostering a pregnancy. However, some young females are able to overcome this hindrance and produce viable pregnancies during thermo stress events. Furthermore, it has been coming to light that seasonality also impacts the male contribution; sperm. The main objective of our proposal is to comprehensively evaluate the female and male physiological aspects and the underlying transcriptional pathways that contribute to seasonal inefficiency in swine providing concrete evidence for future therapeutics. Outcomes of this research will provide opportunities to develop applications for 1) use of frozen/thawed semen collected during cool-season to offset thermo-stress events in males and/or females and 2) dietary supplements for boars that may alter seminal gene transcripts for improved fertility.

Approach:
Semen will be collected from boars during hot- and cool- season and either used immediately, fresh, or cryopreserved for later use, frozen/thawed. Representative sperm from these collections (a. fresh, cool; b. fresh, hot; c. frozen/thawed, cool; and d. frozen/thawed, hot) will be evaluated for transcript response in genes that have been previously identified as up- or down-regulated in response to season or within the methylation pathway. Collected semen will be used to breed gilts during cool- or hot- seasons and pregnancy response and litter traits will be evaluated through 50 days of gestation. Test gilts will be monitored beginning 24 days post-breeding for spontaneous abortions alongside contemporary controls (gilts that will have been bred following the USMARC SOP of an observed estrus and 2 inseminations).